This brief summarizes “Spatial ecology of krill, micronekton, and top predators in the central California Current: Implications for defining ecologically important areas” by Santora et al., which was published in the journal Progress in Oceanography.
What is the importance of eastern boundary upwelling ecosystems?
Eastern boundary upwelling ecosystems are areas of extraordinary productivity and biodiversity, making them optimal for fisheries. Unfortunately, they are among most heavily-impacted ecosystems in the world; mankind is exhausting fish populations, changing food web dynamics, and altering natural habitats. Off the California coast, the Gulf of the Farallones region (from Point Sur to Point Arena) is extremely important; it is home to the largest seabird colony in the continental US. It has high biological diversity despite the fact that in the past, marine species in this area have seen tremendous exploitation. Today, the Gulf of the Farallones continues to be heavily fished even though many sought-after species are depleted.
What are micronekton species?
Micronekton species include krill, forage fish, and squid between 2 and 10 cm that are prey for predatory seabirds, marine mammals, and larger fish (e.g. commercially important salmon and rockfish). These species serve as a link between abiotic elements of an ecosystem and the success of upper-level species, so they are ideal indicators of the relationship between habitat characteristics and biota.
What did we do?
We investigated the connection between the seascape (spatial organization of hydrographic conditions), micronekton productivity and, ultimately, the abundance and spatial distribution of seabirds and mammals. Using integrated data from 20 years of shipboard surveys, we investigated how:
– hydrographic conditions relate to micronekton abundance (and latitudinal regionalization of species)
– micronekton and top predator species relate to life history aspects of the organisms and principal physical aspects of the environment
What did we conclude?
Our analysis showed significant correlation between physical characteristics, primary productivity, and mid-to-upper level predators. We used this information to identify five areas of ecological significance along the California coast based on both environmental and micronekton species assemblages. These areas, intended to be representative regions for ecosystem-based approaches to marine spatial management, share common characteristics; all were located on the continental shelf downstream from upwelling areas, had high chlorophyll a and krill concentrations, and shallow pycnoclines.
The ecologically important areas we defined should be used only for the specific seasons studied and should be applied only in a broad manner. Also, the significant seasonal and yearly variability in life cycle and migratory patterns of species must be considered.